Concrete swimming pool walls have been made with both reusable forms and with forms that remain as a part of the swimming pool walls. For example, U.S. Pat. No. 4,818,142 to Cochran discloses reusable swimming pool wall forms that are erected within a ground evacuation. Concrete is poured between the wall forms and the evacuation to form a pool wall. The wall forms are removed to expose an inside surface of the pool wall which is subsequently covered with a vinyl liner.
However, such precise evacuation, which is required to maintain a reasonably uniform pool wall thickness, is exceptionally difficult with conventional evacuation equipment and is impractical in some soils that tend to shift. Erection of the wall form also makes the closely spaced evacuation subject to cave-ins that can require time-consuming repairs.
U.S. Pat. No. 3,748,810 to Mattingly discloses reusable swimming pool wall forms that include outside as well as inside wall forms. The outside wall forms are erected first within an evacuation site. After leveling the outside wall forms, the inside wall forms are connected to the outside wall forms with so-called "ty-cone assemblies" and support straps. An upper portion of the outside wall forms is shaped to enclose, together with the inside wall forms, an enlarged space that is used to form a surrounding deck. The inside wall forms are removed first to enable the inside surface of the swimming pool wall to be cleaned and painted. The outside wall forms remain in place while the inside surface of the pool is treated but are removed prior to backfilling the remaining evacuation.
Although the outside wall forms allow the evacuation to be made with customary precision, a large evacuation is needed to provide sufficient access space to disassemble the outside wall forms after the pool wall has sufficiently cured. The disassembly of the outside wall forms within the remaining space of the evacuation is difficult and time consuming. Forms for both the inside and outside surfaces of pool walls are also expensive to maintain, store, and transport to pool construction sites.
Swimming pool wall forms that remain as exterior surfaces of concrete swimming pool walls are known, for example, from my U.S. Pat. No. 4,407,102. Both the inside and the outside wall forms are made from continuous strips of a resin material. However, the resin material of the inside wall forms is reinforced with fiber glass to resist bowing from the weight of poured concrete. The inside wall forms are also reinforced by vertical channels enclosing T-head stakes. Vertical braces are connected to the outside wall forms, and the T-head stakes and the vertical braces are interconnected by latches.
Although my permanent wall forms are easy to erect and require no disassembly, the inside and outside wall forms of resin material along with the supporting channels, stakes, braces, and latches contribute to a high cost in materials for making the pool walls. The inside wall forms are particularly expensive. In addition to providing structural strength necessary for supporting poured concrete without bowing, the inside wall forms must be waterproof and have a good appearance. The T-head stakes supporting the inside wall forms are also more costly than conventional bar materials providing similar reinforcement after the pool wall has cured.
U.S. Pat. No. 3,468,088 to Miller discloses another example of a swimming pool wall form in which the inside wall form is a continuous sheet reinforced by a fiber glass material, and the outside wall form is a continuous sheet of resin material. A series of H-shaped vertical supports interconnect the two sheets. Channels attached to the fiber glass sheet engage the H-shaped supports with an interlock. Removable rods hold the sheet of resin material within pockets of the H-shaped supports.
The resin sheeting can be removed and presumably reused as another outside wall form. However, the much more expensive fiber glass sheet and reinforcing structures remain as a part of the pool wall. Also, the H-shaped supports separate the concrete into discrete sections that can weaken the pool wall.